1. Field of the Invention
The present invention relates to volumetric flow controls for aerosol samplers or classifiers which maintain inlet flow volume at a desired level.
2. Description of the Prior Art
Various types of aerosol classifier been advanced, and the assignee of the present application is the Licensee of U.S. Pat. No. 4,670,135, which illustrates a nozzle type high volume virtual impactor. The device shown in U.S. Pat. No. 4,670,135 is the type of device utilizing the present volumetric flow control.
Other prior art classification devices have used hot wires for sensing flow, which provides mass flow control, and sensors such as critical venturi have been used for controlling mass flow in inlets to some types of classifiers. However, the operation of the classifiers of the virtual impactor type is flow volume dependent, and the present invention provides a way of controlling volumetric flow simply, easily, and reliably.